over time and determine direction of rotation. In addition, it can capture a running estimate of the
velocity of the encoder wheel. The input frequency of the QEI inputs may be as high as 1/4 of the
processor frequency (for example, 30 MHz for a 120-MHz system).
The TM4C1294NCPDT microcontroller includes one QEI module providing control of one motor
with the following features:
■ Position integrator that tracks the encoder position
■ Programmable noise filter on the inputs
■ Velocity capture using built-in timer
■ The input frequency of the QEI inputs may be as high as 1/4 of the processor frequency (for
example, 12.5 MHz for a 50-MHz system)
■ Interrupt generation on:
– Index pulse
– Velocity-timer expiration
– Direction change
– Quadrature error detection
1.3.8 Analog
The TM4C1294NCPDT microcontroller provides analog functions integrated into the device, including:
■ Two 12-bit Analog-to-Digital Converters (ADC), with a total of 20 analog input channels and each
with a sample rate of two million samples/second
■ Three analog comparators
■ On-chip voltage regulator
The following provides more detail on these analog functions.
1.3.8.1 ADC (see page 1053)
An analog-to-digital converter (ADC) is a peripheral that converts a continuous analog voltage to a
discrete digital number. The TM4C1294NCPDT ADC module features 12-bit conversion resolution
and supports 20 input channels plus an internal temperature sensor. Four buffered sample
sequencers allow rapid sampling of up to 20 analog input sources without controller intervention.
Each sample sequencer provides flexible programming with fully configurable input source, trigger
events, interrupt generation, and sequencer priority. Each ADC module has a digital comparator
function that allows the conversion value to be diverted to a comparison unit that provides eight
digital comparators.
The TM4C1294NCPDT microcontroller provides two ADC modules, each with the following features:
■ 20 shared analog input channels
■ 12-bit precision ADC
■ Single-ended and differential-input configurations
June 18, 201476
Texas Instruments-Production Data
Architectural Overview
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